For Luck, the ex-teacher — Vic Fangio — becomes the opponent

On Tuesday, 49ers defensive coordinator Vic Fangio recalled how Colts quarterback Andrew Luck would occasionally drop in his office during their season together at Stanford to pick his brain on football matters.

Today, Luck, four days away from facing Fangio’s defense, joked that he should have been even more focused during those chats in 2010.

“I wish I’d paid more attention to those conversations now, I guess,” Luck said. “Coach Fangio was a great coach when I was at Stanford. Guys really loved him. He did so much for our defense there. I think as a quarterback – his door was always open for anyone to come talk to him.

“So every now and then I would have the opportunity to walk in and say hi. They whipped our butts every now and then in practice, so just figuring out ‘Why is the defense doing so well? What are our weaknesses? What are my weaknesses?’”

Three years after their season together at Stanford, Fangio will hope to uncover whatever weaknesses Luck possesses when Indianapolis visits Candlestick Park on Sunday. Jim Harbaugh, who recruited Luck to Stanford, said he didn’t pick up on many areas of his game that could be exploited during their three seasons together.

“There’s not a lot of weaknesses that he has,” Harbaugh said. “He’s a top-notch player. We’re going to have to be very sound, very good.”

The No. 1 overall pick in the 2012 draft, Luck led the Colts to an 11-5 record as a rookie while ranking seventh in the NFL in passing yards (4,374) and 14th in touchdown passes (23). There were some growing pains, however: Luck was tied for third in interceptions (18) and his passer rating (76.5) ranked 26th.

This season, he’s thrown one interception in two games and posted a 96.7 passer rating for the 1-1 Colts.

In his return to the Bay Area, he’ll face a defense that will look similar in scheme to the unit he faced in practices at Stanford as a junior in 2010. A key difference? That Division I defense didn’t have Patrick Willis … or Justin Smith … or NaVorro Bowman.

“There is some carryover in the basic shape of everything,” Luck said. “But this is a different ballgame. The players on the Niners defense are unbelievable. A lot of Pro Bowl players out there. A lot of studs. We know we’re going to have our hands incredibly full.”

Luck has a few teammates who can provide insight on San Francisco’s defense. A pair of ex-49ers, defensive end Ricky Jean Francois and outside linebacker Cam Johnson, are in Indianapolis. In addition, former Stanford offensive coordinator Pep Hamilton has the same role with the Colts.

Luck said it would be fun to reconnect with his college coaches Sunday. And he appreciated Fangio’s role in furthering his football education.

“He was always very accommodating,” Luck said. “And always very patient with what seemed to be a very young, snot-nosed quarterback coming in and trying to learn a little bit about defenses.”